NEET Structure of Atom — Set 18

Question 1

The frequency of a photon is $ 7.5 \times 10^{14} \, \text{Hz} $. What is its energy in joules? ($ h = 6.626 \times 10^{-34} \, \text{J s} $)

Accepted Answer

Energy $ E = h v = 6.626 \times 10^{-34} \times 7.5 \times 10^{14} = 4.9695 \times 10^{-19} \, \text{J} $.

Question 2

The uncertainty in velocity of a proton is $ 2.0 \times 10^5 \, \text{m s}^{-1} $. What is the minimum uncertainty in its position? ($ h = 6.626 \times 10^{-34} \, \text{J s} $, $ m_p = 1.67 \times 10^{-27} \, \text{kg} $)

Accepted Answer

$ \Delta p = m_p \Delta v = 1.67 \times 10^{-27} \times 2.0 \times 10^5 = 3.34 \times 10^{-22} \, \text{kg m s}^{-1} $. $ \Delta x \geq \frac{h}{4\pi \Delta p} = \frac{6.626 \times 10^{-34}}{4 \times 3.14 \times 3.34 \times 10^{-22}} = 1.58 \times 10^{-13} \, \text{m} $.

Question 3

A metal has a work function of $ 3.2 \, \text{eV} $. What is the kinetic energy of an electron ejected by light of wavelength $ 350 \, \text{nm} $? ($ h = 6.626 \times 10^{-34} \, \text{J s} $, $ c = 3.0 \times 10^8 \, \text{m s}^{-1} $, $ 1 \, \text{eV} = 1.6 \times 10^{-19} \, \text{J} $)

Accepted Answer

$ E = \frac{hc}{\lambda} = \frac{6.626 \times 10^{-34} \times 3.0 \times 10^8}{350 \times 10^{-9}} = 5.6794 \times 10^{-19} \, \text{J} = 3.5496 \, \text{eV} $. $ W_0 = 3.2 \, \text{eV} $. $ KE = 3.5496 - 3.2 = 0.3496 \, \text{eV} = 5.5936 \times 10^{-20} \, \text{J} $.

NEET Chemistry: Structure of Atom — Practice Set 18

Q1. The frequency of a photon is \( 7.5 \times 10^{14} \, \text{Hz} \). What is its energy in joules? (\( h = 6.626 \times 10^{-34} \, \text{J s} \))

Q2. The uncertainty in velocity of a proton is \( 2.0 \times 10^5 \, \text{m s}^{-1} \). What is the minimum uncertainty in its position? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( m_p = 1.67 \times 10^{-27} \, \text{kg} \))

Q4. The energy of an electron in the second orbit of a hydrogen atom is \( -5.45 \times 10^{-19} \, \text{J} \). What is its energy in the fourth orbit?

Q5. An electron in a hydrogen atom is excited to \( n = 4 \). How many possible emission lines can it produce?

Q6. Which of the following radiations has the highest frequency?

Q7. Which of the following has the same number of neutrons as an atom with 12 protons and mass number 24?

Q9. The ratio of the kinetic energy of an electron in the first orbit of \( \text{H} \) to the second orbit of \( \text{He}^+ \) is: (\( v_1 \) for H = \( 2.19 \times 10^6 \, \text{m s}^{-1} \), \( m_e = 9.1 \times 10^{-31} \, \text{kg} \))

Q10. The uncertainty in position of an electron is \( 2.0 \times 10^{-10} \, \text{m} \). What is the minimum uncertainty in its momentum? (\( h = 6.626 \times 10^{-34} \, \text{J s} \))